Alcohol use is cited as a risk factor for exposure to HIV infection through risky sexual behavior, especially among adolescents. From Social Cognitive Theory, positive outcome expectancies about the use of alcohol have often been presented as a critical aspect of alcohol use. Yet little is known about how they might be related to different aspects of HIV risk. Using latent growth curve modeling with data from 292 American Indian youth across seven years, both alcohol use and positive expectancies increased significantly; a lower-risk group showed significantly slower increases in both. Changes in alcohol use and outcome expectancies were significantly interrelated, providing support for reciprocal influence between the two constructs. Positive alcohol outcome expectancies may provide a preventive intervention point worthy of further consideration as influencing alcohol use and lowering HIV sexual risk among adolescents.